Crossfire Hurricane (FBI investigation)

Crossfire Hurricane was the code name for the counterintelligence investigation undertaken by the Federal Bureau of Investigation (FBI) from July 31, 2016, to May 17, 2017, into links between Donald Trump's presidential campaign and Russia and "whether individuals associated with Trump's presidential campaign were coordinating, wittingly or unwittingly, with the Russian government's efforts to interfere in the 2016 U.S. presidential election". Trump was not personally under investigation until May 2017, when his firing of FBI director James Comey raised suspicions of obstruction of justice, which triggered the Mueller investigation.

Source: Wikipedia — Crossfire Hurricane (FBI investigation) (CC BY-SA 4.0)